1. Field of the Invention
The present invention relates to a process for producing L-tryptophan using Coryneform bacteria which have been constructed by a recombinant DNA technique.
2. Description of the Related Art
In a process for producing L-tryptophan using microorganisms, where it is attempted to produce L-tryptophan using carbohydrates such as glucose or the like as raw materials, wild strains do not produce L-Tryptophan outside of cells and thus, there is known a process which comprises artifically causing mutation of wild strains in order to impart L-tryptophan productivity ot the wild strains.
As hitherto known mutants having L-tryptophan productivity, there are known mutants of the genus Brevibacterium, Microbacterium or Corynebacterium which are resistant to 5-methyltryptophan (U.S. Pat. No. 3,700,559); mutants of the genus Corynebacterium which require tyrosine and phenylalanine and are resistant to phenylalanine antogonists (Published Examined Japanese Patent Application No. 10937/76); mutants of the genus Bacillus which are resistant to 5-fluorotryptophan (published Unexamined Japanese Patent Application No. 85289/74); mutants of the genus Brevibacterium which are resistant to 5-methyltryptophan and m-fluorotryptophan (Published Unexamined Japanese Patent Application No. 42091/75); and others.
On the other hand, some attempts to utilize recombinant DNA techniques different from the abovementioned breeding involving mutations have also been reported recently. For example, in Appl. Environ. Microbiol., 38 (2), 181-190 (1979), it is described that a particular mutant of Escherichia coli containing a plasmid bearing a trp E472 gene of Escherichia coli produces approximately 1.3 g/l of L-tryptophan. Further, it is mentioned in "Fermentation Technology Association, Japan, Summary of Lectures in the 1980th Conference," page 170 (1980) that a mutant of Escherichia coli containing a plasmid having incorporated therein the tryptophan operon of Escherichia coli produced 360 mg/l of L-tryptophan.
Furthermore, it is mentioned in Published Unexamined Japanese Patent Application No. 208994/82 that L-tryptophan is produced using a microorganism belonging to the genus Bacillus which is constructed by a recombinant DNA technique.
On the other hand, many processes for producing L-tryptophan using anthranilic acid or indole as a raw material are know (for example, Published Examined Japanese Patent Application Nos. 16955/71, 46348/72 and 29584/82, Published Unexamined Japanese Patent Application Nos. 00785/73, 87085/73 and 95484/75, etc.)
Further, there is also known a process for producing L-tryptophan from indole or anthranilic acid using bacteria belonging to the genus Bacillus by a recombinant DNA technique (Published Unexamined Japanese Patent Application No. 89194/73).